Step machine



FIG. 1 is a perspective view of a step machine showing the new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a right side elevational view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The broken lines in FIG. 7 illustrate portions of the step machine which form no part of the claimed design. 

The ornamental design for a step machine, as shown and described. 